Compared with our lowly 350 olfactory receptors in humans, rats and mice have over 1200, essential in their mostly scent-guided world. As such, the social behaviour of rats and mice is influenced by pheromones - chemical factors that elicit a response in the same species. Less well studied are the effects of kairomones, chemical factors that elicit behavioural response across different species. An example of this complex interspecific communication has recently been discovered between rats and mice and their predators: a compound found in high concentrations in the urine of carnivorous mammals produces an instinctive avoidance response in rats and mice.
The kairomone 2-phenylethylamine, a product of protein metabolism, is found at a concentration over 3000 times greater in carnivorous mammals than in herbivorous mammals. Due to its volatility (particles are easily suspended in the air), these high levels of 2-phenylethylamine can de detected from great distances. When it reaches the nose of a rat or mouse, the kairomone activates trace amine-associated olfactory receptor TAAR4, causing an innate avoidance response. While this is a key aid in survival for rats and mice, meanwhile, we would walk on by oblivious, as we completely lack the gene for TAAR4. The mechanism by which chemical receptors are translated via neural circuits to behaviours is a fascinating subject, as yet unresolved.
Ref: D. M. Ferrero et al. (2011) Detection and avoidance of a carnivore odor by prey. Proceedings of the National Academy of Sciences 108(27) 11235-11240 [link]
Source: Flickr / necilbug
![Compared with our lowly 350 olfactory receptors in humans, rats and mice have over 1200, essential in their mostly scent-guided world. As such, the social behaviour of rats and mice is influenced by pheromones - chemical factors that elicit a response in the same species. Less well studied are the effects of kairomones, chemical factors that elicit behavioural response across different species. An example of this complex interspecific communication has recently been discovered between rats and mice and their predators: a compound found in high concentrations in the urine of carnivorous mammals produces an instinctive avoidance response in rats and mice.The kairomone 2-phenylethylamine, a product of protein metabolism, is found at a concentration over 3000 times greater in carnivorous mammals than in herbivorous mammals. Due to its volatility (particles are easily suspended in the air), these high levels of 2-phenylethylamine can de detected from great distances. When it reaches the nose of a rat or mouse, the kairomone activates trace amine-associated olfactory receptor TAAR4, causing an innate avoidance response. While this is a key aid in survival for rats and mice, meanwhile, we would walk on by oblivious, as we completely lack the gene for TAAR4. The mechanism by which chemical receptors are translated via neural circuits to behaviours is a fascinating subject, as yet unresolved.Ref: D. M. Ferrero et al. (2011) Detection and avoidance of a carnivore odor by prey. Proceedings of the National Academy of Sciences 108(27) 11235-11240 [link]](http://24.media.tumblr.com/tumblr_lnwzzc8WZ71qkrbaho1_400.jpg)